Functional Redundancy of Paralogs of an Anaphase Promoting Complex/Cyclosome Subunit in Caenorhabditis elegans Meiosis

Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Genetics (Impact Factor: 5.96). 10/2010; 186(4):1285-93. DOI: 10.1534/genetics.110.123463
Source: PubMed


The anaphase promoting complex/cyclosome (APC/C) mediates the metaphase-to-anaphase transition by instructing the ubiquitination and turnover of key proteins at this stage of the cell cycle. We have recovered a gain-of-function allele in an APC5 subunit of the anaphase promoting complex/cyclosome. This finding led us to investigate further the role of APC5 in Caenorhabditis elegans, which contains two APC5 paralogs. We have shown that these two paralogs, such-1 and gfi-3, are coexpressed in the germline but have nonoverlapping expression patterns in other tissues. Depletion of such-1 or gfi-3 alone does not have a notable effect on the meiotic divisions; however, codepletion of these two factors results in meiotic arrest. In sum, the two C. elegans APC5 paralogs have a redundant function during the meiotic divisions.

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    • "Identical meiotic arrest phenotypes have been generated through RNAi mediated depletion of any of the following: (a) any 1 of 11 different APC/C subunits (Davis et al. 2002; Dong et al. 2007; Kops et al. 2010; Green et al. 2011), (b) the CDC20 ortholog, fzy-1, or (c) any one of several proteasome subunits or the two ubiquitin genes, ubq-1 and ubq-2 (Sonnichsen et al. 2005). To date, the less severe RNAi depletion phenotypes of the Apc10-like subunits remain poorly characterized, and those of the two Apc5-like subunits (SUCH-1 and GFI-3) suggest that they function redundantly during meiosis (Stein et al. 2010). Yet despite the many new insights that these various biochemical, genetic, and structural studies are revealing in regard to the mechanistic details of the APC/C, both the composition and regulation of the APC/C remain incompletely understood, particularly as APC/C studies are extended into additional species and cell types. "
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    ABSTRACT: In the nematode Caenorhabditis elegans, temperature-sensitive mutants of emb-1 arrest as one-cell embryos in metaphase of meiosis I in a manner that is indistinguishable from embryos that have been depleted of known subunits of the anaphase-promoting complex or cyclosome (APC/C). Here we show that the emb-1 phenotype is enhanced in double mutant combinations with known APC/C subunits and suppressed in double mutant combinations with known APC/C suppressors. In addition to its meiotic function, emb-1 is required for mitotic proliferation of the germline. These studies reveal that emb-1 encodes K10D2.4, a homolog of the small, recently discovered APC/C subunit, APC16.
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    • "However, subjecting such-1 mutant animals simultaneously to gfi-3(RNAi) and such-1(RNAi) results in the vast majority of embryos being arrested in meiosis I (Stein et al. 2010, accompanying article in this issue), indicating that the two APC5 components act largely redundantly at this stage. Therefore, in contrast to the situation in Drosophila, where some APC/C substrates are turned over in embryos harboring a genetic null mutation in the sole APC5 gene ida (Bentley et al. 2002), the available evidence indicates that in C. elegans APC5 is essential for canonical APC/C function. "
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    ABSTRACT: The anaphase promoting complex/cyclosome (APC/C) triggers the separation of sister chromatids and exit from mitosis across eukaryotic evolution. The APC/C is inhibited by the spindle assembly checkpoint (SAC) until all chromosomes have achieved bipolar attachment, but whether the APC/C reciprocally regulates the SAC is less understood. Here, we report the characterization of a novel allele of the APC5 component SUCH-1 in Caenorhabditis elegans. We find that some such-1(t1668) embryos lack paternally contributed DNA and centrioles and assemble a monopolar spindle in the one-cell stage. Importantly, we show that mitosis is drastically prolonged in these embryos, as well as in embryos that are otherwise compromised for APC/C function and assemble a monopolar spindle. This increased duration of mitosis is dependent on the SAC, since inactivation of the SAC components MDF-1/MAD1 or MDF-2/MAD2 rescues proper timing in these embryos. Moreover, partial depletion of the E1 enzyme uba-1 significantly increases mitosis duration upon monopolar spindle assembly. Taken together, our findings raise the possibility that the APC/C negatively regulates the SAC and, therefore, that the SAC and the APC/C have a mutual antagonistic relationship in C. elegans embryos.
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